U.S. patent number 4,776,411 [Application Number 07/028,990] was granted by the patent office on 1988-10-11 for fluid flow control for drag bits.
This patent grant is currently assigned to Smith International, Inc.. Invention is credited to Kenneth W. Jones.
United States Patent |
4,776,411 |
Jones |
October 11, 1988 |
Fluid flow control for drag bits
Abstract
A drag type drilling bit having a plurality of radially disposed
raised lands on the bit face is disclosed. A multiplicity of
polycrystalline diamond compacts are strategically disposed on the
raised lands. At least a pair of lands are joined at the outside
periphery of the bit thereby closing the valley formed between the
lands, thus forming a plenum for drilling fluid that exits the bit
interior through ports or nozzles communicating therewith. Highly
turbulent fluid confined in the plenum continually scrubs and
scavenges the hole bottom while simultaneously and uniformly
cooling and cleaning the PDC cutters during operation of the bit in
a borehole.
Inventors: |
Jones; Kenneth W. (Kingwood,
TX) |
Assignee: |
Smith International, Inc.
(Newport Beach, CA)
|
Family
ID: |
21846631 |
Appl.
No.: |
07/028,990 |
Filed: |
March 23, 1987 |
Current U.S.
Class: |
175/393;
175/429 |
Current CPC
Class: |
E21B
10/006 (20130101); E21B 10/55 (20130101); E21B
10/567 (20130101); E21B 10/602 (20130101) |
Current International
Class: |
E21B
10/00 (20060101); E21B 10/46 (20060101); E21B
10/54 (20060101); E21B 10/56 (20060101); E21B
10/60 (20060101); E21B 010/60 () |
Field of
Search: |
;175/329,339,340,393,417,418,394,395,410 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Massie, IV; Jerome
Assistant Examiner: Kisliuk; Bruce M.
Attorney, Agent or Firm: Upton; Robert G.
Claims
What is claimed is:
1. A drag type drilling bit comprising:
a bit body forming a first pin end and a second cutting end, said
first pin end is open to drilling fluid that is transmitted through
an attachable drillstring, the pin end communicates with a fluid
chamber formed by said bit body, at least two pairs of
substantially radially disposed raised lands are formed by said
second cutting end of said bit, said raised lands being joined near
an axial centerline of said bit and adjacent an outer peripheral
edge of said bit body thereby forming at least a pair of plenum
chambers thereby, said plenum chambers being spirally disposed,
said plenum chambers taper in depth radially from the center of the
bit to the outer peripheral edge of the bit, said plenum chambers
being surrounded by a low pressure area in a borehole annulus
surrounding the bit;
a multiplicity of cutting elements are strategically positioned and
fixedly attached to the raised lands; and
one or more ports are formed in said second cutting end of said bit
body, said ports communicate between said chamber formed by said
bit body and the plenum chambers formed by said raised lands, said
fluid exits said one or more ports and is distributed within said
plenum chambers thereby scavenging a borehole bottom while
uniformly cooling and cleaning said multiplicity of cutting
elements during drag bit operation in said borehole.
2. The invention as set forth in claim 1 wherein the plenum
chambers taper in depth from a leading edge formed by said raised
lands nearest said axial centerline of said bit to a trailing edge
formed by said raised lands nearest said outer peripheral edge of
said bit.
3. The invention as set forth in claim 1 wherein the plenum
chambers cover about fifty percent of the borehole bottom area.
4. The invention as set forth in claim 1 wherein said cutting end
forms three plenum chambers, said plenum chambers cover about
ninety percent of the borehole bottom in a radial direction from
said axial centerline of said bit.
5. The invention as set forth in claim 4 wherein the three plenum
chambers cover about fifty percent of the borehole bottom area.
6. A drag type diamond drilling bit comprising:
a bit body forming a first pin end and a second cutting end, said
fist pin end is open to drilling fluid that is transmitted through
an attachable drillstring, the pin end communicates with a fluid
chamber formed by said bit body, at least six substantially
radially disposed raised lands are formed by said second cutting
end of said bit, one pair each of raised lands being contained in
one hundred and twenty degree radial segments formed by said second
cutting end, each pair of said raised lands being joined near an
axial centerline of said bit and adjacent a peripheral edge of said
bit, said joined raised lands forming three plenum chambers
thereby, each of said plenum chambers is spirally disposed, said
plenum chambers taper in depth from a leading edge formed by said
raised lands nearest said axial centerline of said bit to a
trailing edge formed by said raised lands nearest said outer
peripheral edge of said bit, said plenum chamber being surrounded
by a lower pressure area in a borehole annulus surrounding the
bit;
a multiplicity of diamond cutting elements are strategically
positioned and fixedly attached to the raised lands, said cutting
elements protruding beyond a planar face formed by said raised
lands such that a minimum space is formed between said cutting
elements and a borehole bottom of said borehole; and
at least one nozzle is attached within at least one port formed in
said second cutting end of said bit body, said port communicates
between said chamber formed within said bit body and the plenum
chambers formed by said raised lands, said fluid exits and nozzle
and is distributed within said plenum chamber thereby scavenging
said borehole bottom while uniformly cooling and cleaning each of
said multiplicity of cutting elements, said fluid being accelerated
past said cutting elements through said minimum space formed
between said cutting elements and said borehole bottom during drag
bit operation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to diamond type drag bits that utilize
hydraulic energy to enhance earth formation penetration rates.
More particularly, this invention relates to diamond type drag bits
having a superior means to utilize hydraulic energy passing through
the bit to cool and clean as well as scavenge a borehole bottom
during rock bit operation.
2. Description of the Prior Art
There are a number of diamond type drag bit patents that address
the problem of cooling and cleaning diamond cutting elements during
rock bit operation.
For example, U.S. Pat. No. 4,253,533, assigned to the same assignee
as the present invention, describes a diamond studded insert drag
bit having a multiplicity of individual diamond insert cutter
blanks inserted in the face of the bit. The diamond insert blanks
are so positioned to maximize penetration of the bit in a borehole.
The bit further includes a pair of wear pads adjacent the several
diamond insert cutter blanks, the wear pads serving to limit the
insert penetration depth while channeling the flow of drilling mud
emanating from fluid passages formed in the face of the bit. The
wear pads seal off a portion of the borehole bottom, thereby
directing hydraulic fluid across the face and over each of the
strategically positioned diamond cutter blanks.
While this patent has proven satisfactory in operation, it has not
provided an even distribution of crossflow fluid to each of the
diamond cutter blanks. For example, energy velocity is dissipated
as flow reaches the outer peripheral edge of the bit, thus some of
the insert blanks near the gage of the bit tend to be more effected
by heat buildup and the like.
Another patent, U.S. Pat. No. 4,246,977, also assigned to the same
assignee as the present invention, describes a diamond studded
insert drag bit having a multiplicity of individual diamond insert
cutter blanks inserted in the face of the bit. The diamond blanks
are so positioned to maximize penetration of the bit in a borehole.
The bit further includes fluid passages strategically located in
the bit face to provide uniform flow, cooling, and continuous
cleaning of each of the diamond cutter insert blanks. The fluid
passages are so sized to cause minimum bit pressure drop. While
this invention did evenly distribute fluid over the diamond
cutters, the design did not adequately scavenge the borehole bottom
to efficiently remove detritus therefrom.
Another prior art patent, U.S. Pat. No. 4,492,277, describes a drag
bit for drilling a rock formation having a bit face matrix for
supporting a plurality of cutters, the matrix having one or more
fluid passages for discharging a fluid to flow over the bit face.
To enhance the cooling and cleaning of the plurality of cutters,
the bit face matrix includes a "crow's foot" type port that directs
fluid into a restricted area formed between the bit face and the
formation. A high velocity radial fluid flow across the bit face
matrix is the desired effect. The fluid flow prevents debris from
accumulating on the plurality of cutters thus providing cooling
thereof. The patent teaches improved fluid distribution. A
spiraling type dam structure is illustrated that extends from the
nozzle radially outward over most of the bit face matrix.
This patent does not provide a uniform flow of fluid from the
crow's foot fluid opening to each of the cutters randomly
positioned on the face of the bit.
The present invention overcomes the shortcomings of the foregoing
prior art patents by providing large plenum chambers in the cutting
face of the bit which are adapted to receive fluid from the
interior of the drag bit, thus providing better than fifty percent
borehole bottom coverage with high pressure drilling fluid. A
series of diamond cutters are mounted on the raised lands that
defines and forms each plenum chamber. The highly turbulent fluid
confined within the plenum chambers is then uniformly accelerated
past each of the diamond cutters mounted on the raised lands. The
abundance of turbulent hydraulic energy made available by the large
plenum chambers serves to more aggressively scavenge the borehole
bottom of detritus while simultaneously cleaning and cooling each
of the diamond cutters mounted in the raised lands. Moreover, the
plenum chambers, being surrounded by closely spaced cutter
elements, enable a multiplicity of diamond cutters to be positioned
adjacent the gage of the borehole, thus providing good rock
formation penetrating qualities while providing superior gage
cutting capabilities.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a diamond drag bit
having superior hole cleaning and diamond cutter cooling
capabilities, thereby enhancing rock bit penetration.
More particularly, it is an object of this invention to provide a
diamond drag bit having one or more plenum chambers to accept fluid
directed to the chamber, the plenums being surrounded by raised
lands that support a multiplicity of diamond cutters thereon. Fluid
is accelerated uniformly past each of the diamond cutters thereby
cooling and cleaning each of the cutters.
The drag type drilling bit of the present invention consists of a
bit body that forms a first pin end and a second cutting end. The
first pin end is opened to a source of drilling fluid that is
transmitted through an attachable drillstring. The pin end
communicates with a fluid chamber that is formed by the bit body.
One or more radially disposed raised lands are formed by the second
cutting end of the bit. The raised lands are joined near a
centerline of the bit and adjacent an outer peripheral edge of the
bit body thereby forming at least one plenum chamber thereby. A
multiplicity of diamond cutting elements are strategically
positioned and fixedly attached to the raised lands. One or more
ports are formed in the second cutting end of the bit body, the
ports communicating between the chamber formed within the bit body
and the plenum chamber formed by the raised lands. Fluid or
drilling mud exits the ports and is distributed within the plenum
chamber, thereby scavenging a borehole bottom while uniformly
cooling and cleaning the multiplicity of diamond cutting elements
during drag bit operation.
The aforementioned drag bit may have three plenum chambers that are
shaped in a spiral pattern such that each plenum chamber forms a
first leading edge and a second trailing edge. The bottom of the
plenum chamber formed by the face of the rock bit may vary in
depth, tapering from a leading edge portion towards a trailing edge
portion. Fluid entering the plenum chamber is accelerated from the
leading edge toward the trailing edge through the constricted space
formed between the plenum chamber and the borehole bottom. A series
of axially oriented slots are formed in a wall of the bit body.
Fluid and debris escaping the plenum chambers is directed along
these slots back to the rig floor. In addition, a series of
spirally oriented low pressure troughs may be formed on the face of
the bit in parallel with the plenum chambers. The low pressure
troughs transport fluid and detritus out of the plenums to
relatively large axially aligned debris slots also formed in the
wall of the rock bit body to act as a means to transport a majority
of the borehole cuttings up the drillstring.
An advantage then over the prior art is the means in which fluid is
accelerated past the diamond cutters in a uniform fashion, thus
providing a superior means to scavenge the borehole bottom while
also providing a cooling and cleaning function to each and every
one of the cutters mounted in the raised lands portion surrounding
the plenum chambers.
Yet another advantage of the present invention over the prior art
is the ability to apply much more diamond cutting elements on the
gage of the bit. About one quarter of the multiplicity of closely
spaced diamond cutters attached to the raised lands are positioned
on gage, the remainder of the cutters completing the loop around
the plenum chambers.
The above noted objects and advantages of the present invention
will be more fully understood upon study of the following
description in conjunction with the detailed drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a preferred embodiment of the
present invention, illustrating the spirally oriented plenum
chambers separated and confined by diamond cutter containing raised
lands;
FIG. 2 is a top view of the diamond drag bit cutter, clearly
illustrating each of the plenum chambers ringed by diamond compacts
cutters, each of the chambers having a nozzle positioned
therein;
FIG. 3 is a partially broken away cross-sectional view taken
through 3--3 of FIG. 2 illustrating the drag bit and the means in
which fluid is directed from a chamber formed by the bit body
through a nozzle;
FIG. 4 is a side view of a diamond cutter blank mounted to a stud
which is pressed into the raised lands formed on the cutting face
of the bit;
FIG. 5 is a front view taken through 5--5 of FIG. 4 illustrating a
half-round polycrystalline diamond compact mounted to a cutter
stud;
FIG. 6 is another embodiment of a diamond cutter mounted in the
raised lands;
FIG. 7 is a view taken through 7--7 of FIG. 6 showing a full faced
polycrystalline diamond compacts mounted to a stud;
FIG. 8 is yet another variety of diamond cutter wherein the cutter
is self-sharpening, having first and second diamond faces on a
supporting stud;
FIG. 9 is a view taken through 9--9 of FIG. 8 showing the larger
cutting face of the diamond cutter; and
FIG. 10 is a view taken through 10--10 of FIG. 8 illustrating the
back side of the self-sharpening cutter mounted to a raised land
formed in the cutting face of the bit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST MODE FOR CARRYING
OUT THE INVENTION
Turning now to FIG. 1, the diamond drag bit, generally designated
as 10, consists of a drag bit body 12, shank 14, pin end 16, and a
cutting end 20. A pair of wrench flats 15 are formed in the shank
portion of the bit 10. The wrench flats are designed to accommodate
a bit breaker (not shown) used to disconnect pin end 16 from a
drillstring (also not shown).
The cutting end, generally designated as 20, of bit 10 consists of
a series of raised lands 22, formed by the face of the bit. Raised
lands 22 are joined in pairs near the centerline of the bit body 12
and at the peripheral edge or gage 21 of the bit 10, forming plenum
chambers 28 thereby. The peripheral edge 21 also forms the gage of
the bit 10. Each plenum chamber 28 has at least one port 34 which
communicates with an internal reservoir chamber 18 (FIG. 3) formed
by the bit body 12. Replaceable nozzles 36 may be engaged with each
of the ports 34 formed in the chamber areas of the bit face 20.
The raised lands 22 are preferably shaped in a spiral pattern,
pairs of which form a leading edge 24 and a trailing edge 26. The
plenum chamber 28 may be further refined by tapering the depth of
the chamber from a deep inboard area 30 to a more shallow outboard
area 32 nearest the gage 21 of the bit body 12. With a clockwise
rotation of the drag bit in a borehole, fluid escapes or is
accelerated through nozzle 36 into plenum chamber 28, the turbulent
fluid being further accelerated from the leading edge 24 towards
the trailing edge 26 of the spirally shape chamber. Fluid picks up
impetus both through centrifugal force and the rotational speed of
the bit. The tapering flow path defined between the bottom of the
plenum chamber 28 and a borehole bottom formation 51 (FIG. 4)
assures further fluid accelerated through this narrowing gap prior
to escaping past diamond cutters 52 to the outside of the bit.
A multiplicity of equally spaced and strategically positioned
cutters, generally designated as 50, are mounted onto a planar
surface 23 formed by the raised lands 22. The cutters 50 may be
selected from varying materials and compositions, some of which
will be set forth in detail in the following specification.
Referring specifically to FIGS. 4 and 5, a preferred cutter 52
consists of a half-diameter polycrystalline diamond compact
metallurgically bonded to a tungsten carbide stud that is pressed
or interference fitted into a complementary insert hole 55 formed
in the planar surface 23 of raised land 22. These types of inserts,
particularly those shown in FIGS. 4 through 7, are STRATAPAX
inserts, developed by General Electric Company of Worthington,
Ohio. Referring again to FIG. 1, the STRATAPAX type inserts 52,
with their half-diameter polycrystalline diamond cutters mounted to
the stud, enable the planar surface 23 of raised lands 22 to
maintain a relatively narrow gap (shown as A in FIG. 4) between the
planar surface 23 and a formation borehole bottom indicated as 51.
The height of the diamond cutter and the distance the fluids must
travel from the high pressure plenum to the low pressure annulus
surrounding the bit completely determines the behavior of the fluid
as it escapes the plenum chamber 28. This parameter is the most
critical aspect of the present invention. The borehole bottom, of
course, closes out the chamber 28, enabling the turbulent fluid
flow to be accelerated over the planar surface 23 past each of the
equidistantly spaced cutters 52 fixed within the raised lands
22.
Low pressure collector channels or grooves 40 are shown positioned
substantially parallel to the raised lands 22. The low pressure
collector grooves serve to collect detritus and low pressure fluid
escaping past the cutters to the outside of the rock bit. Each of
the three low pressure collectors shown dump into enlarged gage
relief slots or channels 42 axially aligned along the outer wall 13
of bit body 12.
In addition to the major gage relief channels 42 a multiplicity of
axially aligned escape slots 38 are formed in wall 13 adjacent the
gage surface 21 of bit body 12. The multiplicity of axially aligned
and equidistantly spaced slots 38 serve to receive high pressure
hydraulic fluid escaping past the gage cutters 52 from plenum 28,
thus providing a further path for detritus and low pressure
hydraulic fluid to escape up the borehole to the rig floor.
Turning now to FIG. 2, the cutting face 20 of the diamond drag bit
10 defines preferably three pairs of spirally oriented raised lands
22. The inboard ends of a pair of raised lands 22 connects towards
the centerline of the drag bit while the radially outwardly
extending pairs of raised lands connect again at the peripheral
edge or gage 21 of the bit body 12. A multiplicity of cutting
element 50 are equidistantly spaced around the entire perimeter of
each of the plenum chambers 28 formed in the bit face 20. It can
readily be realized in the view depicted in FIG. 2 that almost half
of the diamond cutters 52 are on gage 21 of the cutter 10. This
feature assures that the bit maintains "in gage" (a minimum
borehole diameter) during the full operating range of the bit. By
entirely surrounding an enclosed plenum chamber with, for example,
equidistantly spaced diamond cutters the entire formation borehole
bottom is assured of being cut without leaving kerfs and valleys in
the borehole bottom. A nozzle 36 is installed in each of the ports
34 to direct a stream of hydraulic fluid into chamber 18 (FIG. 3).
The fluid enters a channel 33 leading from chamber 18 to the nozzle
36. Obviously the nozzle 36 may have different throat diameters so
that the bit may be tailored to match different rock formations and
hydraulic energy available to the bit. Again, the spirally shaped
plenums direct accelerated hydraulic fluid outwardly in all
directions past the multiplicity of diamond cutters extending
beyond the planar surface 23 of raised lands 22. As stated before,
the plenum chamber 28 is preferably tapered from a relatively deep
portion 30 near the centerline of the bit to a relatively shallow
area 32 nearest the peripheral edge or gage 21 of the bit. The
tapering feature of the plenum from deep to shallow, as well as the
rotational and centrifugal energy imparted to the diamond bit
through the drillstring assures high flow velocities as well as
uniform flow to all the diamond cutters. Thus, the diamond cutters
are adequately cooled and cleaned and the borehole bottom scavenged
to assure the best possible penetration rate of the bit 10 as it
works in a borehole therefore minimizing high temperature
degradation of the diamond cutters to maximize cutter life.
The partially cutaway cross section of FIG. 3 illustrates the
replaceable nozzles 36 which, for example, have at their exit end a
series of slots 37 to accept a tool for nozzle installation (not
shown). Each nozzle typically has an O-ring 39 at its base to
prevent internal nozzle erosion. Again, the nozzles feed fluid into
the plenum chambers 28, the turbulent flow of fluid being channeled
between the bottom of the plenum chamber and the borehole bottom 51
as shown in FIG. 4.
For practical purposes, the number of raised lands 22 is divisible
by twos and are arranged so that the bit cutting face 20 is divided
into alternating lands and valleys or grooves. For example, every
other pair of raised lands 22 are joined at the outside diameter or
gage 21 of the bit 10, closing the valley (forming plenum chamber
28) between the two raised lands 22. The plenums 28 cover about
eighty to ninety percent of the borehole bottom 51 radially, which
equates to about forty to fifty percent of the borehole bottom
area. This abundant coverage of borehole bottom permits the highly
turbulent fluid confined within the chambers 28 to continually
scrub and scavenge the hole bottom 51, presenting virgin rock
formation surfaces for the cutting elements 50 to engage and
resulting in higher rates of rock bit penetration.
Turning now to FIGS. 4 through 10, the preferred STRATAPAX type
cutter 52 is shown with a half-circular polycrystalline diamond
compact 54 metallurgically bonded to a stud 53 that is typically
fabricated from tungsten carbide. The stud is interference fitted
within a hole drilled through planar surface 23 of raised lands 22.
These inserts are set deeply within the raised lands 22, thus the
cutting edge exposure beyond planar surface 23 is minimized. This
feature minimizes the gap between the face 20 of the bit 10 and the
formation bottom 51. FIG. 5 shows a front view of the half
polycrystalline diamond compacts 54 as it extends above planar
surface 23. FIG. 6 illustrates a typical STRATAPAX type cutter 56
having a full 360.degree. diamond compact 58 metallurgically bonded
to a stud body 57, the body being interference fitted within a hole
50 drilled in raised lands 22. A counterbore 59 allows the bottom
portion of the diamond compacts to be positioned below the planar
surface 23, thus minimizing the cutter extension beyond the planar
surface while providing backup support for the tungsten carbide
stud body 57. FIG. 7 shows a front view of the full compacts and
its relationship with planar surface 23 of raised lands 22.
FIGS. 8 through 10 illustrate a different embodiment of a cutting
element. The cutting element 70 is basically formed from a tungsten
carbide body. The cutting end of the tungsten carbide cutter 70 is
coated with a layer or layers of diamond surface 72. A diamond
cutting side or leading edge side 72 and a trailing diamond surface
76 is formed on the stud body 70. The area 74 between the diamond
surfaces 72 and 76 is tungsten carbide devoid of the diamond
coating composition. In principle, the cutter is self-sharpening
since the tungsten carbide material 74 is less hard than the
diamond surfaces 72 and 76. The tungsten carbide wears away faster
than the diamomd cutting surfaces 72 and 76, therefore providing
the "self-sharpening" feature. FIG. 9 shows the front or leading
cutting portion 72 which, of course, extends beyond surface 23 of
raised lands 22. FIG. 10 shows the back view illustrating both the
diamond layers 76 and 72 with intermediate tungsten carbide 74
therebetween. The insert is interference fitted within hole 60
formed in raised lands 22.
Other types of cutters 50 may be incorporated on or within planar
surface 23 of raised lands 22. For example, a multiplicity of
chisel type tungsten carbide inserts, well known in the rock bit
industry, may be inserted in the raised lands (not shown).
Moreover, thermally stable polycrystalline diamond (PCD) cutters
may be incorporated that are, for example, anchored within a
tungsten carbide matrix applied to the cutter face 20 of the bit
10. These PCD cutters may be shaped in cylinders, cubes and
triangles for optimum rates of penetration (not shown).
In addition, natural diamonds may be set in a tungsten carbide
matrix and disbursed in random fashion on the planar surface 23 of
raised lands 22.
It will of course be realized that various modifications can be
made in the design and operation of the present invention without
departing from the spirit thereof. Thus, while the principal
preferred construction and mode of operation of the invention have
been explained in what is now considered to represent its best
embodiments, which have been illustrated and described, it should
be understood that within the scope of the appended claims, the
invention may be practiced otherwise than as specifically
illustrated and described.
* * * * *